Method of making two ply tubing



Nov. 25, 1941. s. BLOOMFIELD EIAL METHOD OF MAKING TWO PLY TUBING F 1 d Ap 1 1 1940 20565 filamfz'eld jzkro picted in Figs. 1

Patented Nov. 25, 194i UNITE or svTAres P AT METHOD ()F'MAKING r'wo 'PEY TUBING;

ApplicationA-pril1, 11940,Serial.No; 327,219

1 Claim; (01. 29+1ssi;

or body portion. in cold :rolled steel tube nature of a Welded stainless steel tube.

While the compositions of the core tube the sheath tube may vary within wide limits,

the nature. of a sheathed by, keyed to and expanded into a relatively very thin shell in the.

thecore tube will always be relatively thick and I resistant.

The expanding of the core, and the consequent circumferential stretching of the thin sheath tube is preferably efiected hydraulically, e. g., by subof the core tube to the direct action of liquid under pressure, or by subjecting the said inner surface of the core tube to the expanding action of a suitable hydraulically actuated mandrel.

In the accompanying drawing,

Fig. l is a perspective view of a section of a welded tube of cold rolled steel, suitable for ultimate use as the core element of our improved two ply tubing;

Fig. 2 illustrates how such cold rolled steel tube may be operated upon before being inserted and expanded into its stainless steel sheath;

Fig. 3 is a perspective view of a section of a very thin stainless steel tube which is intended ultimately to become a tightly stretched sheath for the more heavy and less expensive tube deand 2;

Fig. 4 illustrates how the channelled and milled tube of Fig. 2 is inserted into the stainless steel tube of Fig. 3;

Fig. 5 diagrammatically illustrates one method of expanding the core tube, and simultaneously circumferentially stretching the sheath tube, in the manner contemplated by the present invention; and I Fig. 6 diagrammatically illustrates another method of effecting such expansion and circumferential stretching.

concerned I with" thick core tube metai Whereas sheath tube always will be relatively thin and formed. of relatively expensive metal of a left the external and internal,

I21] respectively, extending. longitudinally of the tube.

Fig, 2. diagrammatically illustrateshow W9.

nextfiwork upon a tube of we have chosen to show three .of the milling r011 I 5 of :CIQSSIY' dis: posed .parallel lines, into the external surface of .i

ers," each adapted'to mill .a row the tube varied within wide limits.

In Fig. 3 we have shown a welded tube I! which may be assumed to have been formed, in well known manner, from stainless steel sheet, such tube l1 carrying an internal longitudinally extending flash nib indicated at the welding operation.

With respect to suitable proportions, in the matter of diameter of two and one-half inches (2 and a thickness of one eighth inch and has been encased within a sheath tube I! having an initial thickness of fifteen one thousandths of an inch Naturally, these proportions may be Varied within rather Wide limits.

In forming our improved two ply tube, the core tube In, after being operated upon as depicted in Fig. 2, is inserted into the sheath tube l'!, with the groove [5 of tube It] receiving, as a key, the longitudinally disposed internal flash nib I8 of sheath tube l1. See Fig. 4,

Eur ore-rec; i

flash nibs, n and.

expanding mandrel having Next we proceed to expand the core tube It, and to stretch the sheath tube H around the core tube, in accordance with one or the other of the procedures indicated in Figs. 5 and 6.

In Fig. 5 reference numeral N! indicates a tube a tapered end 20, a cylindrical surface 2| which determines the ultimate interior diameter of the core tube l and a shank 22. Such tube expanding mandrel is adapted to be projected, by any suitable hydraulically actuated mechanism (not shown) in the direction of the plain arrow (Fig. to exl5, and simultaneously stretch a around such core tube, when pand the core tube the sheath tube l1 7 such core tube I0 is subjected toa reactive force acting in the direction of the feathered arrows (Fig. 5). It will not be necessary toillustrate the member which exerts the aforesaid reactive force upon the core necessary to illustrate the devices whereby the expanding mandrel is projected into, and withdrawn from, the core tube In after expanding the latter, since the functioning of tube expanding mandrels, and the'mechanism for operating same, are now well understood by persons skilled in the art to which our invention relates.

Naturally, a mandrel of the kind indicated in Fig. 5 will function to eliminat the interior flash nib II of the core tube Ill. It will be noted in Fig. 4 that the flash I8 is of substantially the same area in cross section as the groove l5 in the corresponding relatively thick tube W. This factor is important, since the relatively thin walled tube l1 would be distorted by any material disparity in size between the flash and its receiving groove.

When following the procedure diagrammatically illustrated in Fig. 6, we effect the necessary expanding of the core tube It), and the consequent stretching of the sheath tube lI around the core tube ID, by introducing liquid 23, under pressure, into the interior of core II! in a manner also well known to the class of persons to whom this specification is directed. In view of the tube l0. Neither will it be common use, at this date, of hydraulic pressure to expand tubes and other hollow metallic devices, it is believed that the purely diagrammatic showing of Fig. 6 will be ample for the purposes of the present specification.

The interior flash nib may be removed from any tube by pulling or projecting a suitable cutting tool through such tube, the tool being operated hydraulically or otherwise.

It should be understood that the method of the present invention may be utilized in providing a cold rolled steel tube with a stainless steel lining, by reversing the relative position of the tubes whenever it is desired to provide a two ply tubing with the stainless steel ply on the interior. In such case the groove to receive the flash would be on the inner face of the thicker or base metal tub It), and the flash on the stainless steel tube would project outwardly from the outer surface of said tube.

Having thus illustrated and described our invention, what we regard as new and desire to secure by Letters Patent of the United States is:

The method of making two ply tubing which comprises forming a relatively thin walled tube of weldable sheet metal, of welding a longitudinal seam in said tube to form a projecting welding flash, of cutting a groove longitudinally in a relatively thick walled second tube to receive said flash, said groove being of not less cross sectional area than said welding flash, said second tube having a diameter to have free relative telescoping fit with the first tube, of telescopically interfitting the tubes, one within the other, with the longitudinal groove in the thicker tube in radial registry with the flash of the other tube, and of thereafter expanding the inner of said tubes into intimate interfitted relationship with the other tube, whereby the flash is interfitted in said groove without distorting either tube from its tubular form.

SAMUEL BLOOMFIELD. DANIEL BLOOMFIELD. HAROLD BLOOMFIELD. 

